Asidepa

Test

Dipole impedance graphing

Thanks for the plot of Dipole antenna impedances; it is much appreciated. Similar plots are available in web searches, but not in Smith Chart format. Are you able to post that same data plotted on a Smith Chart, please? (You can reply to me, Asidepa.) — Preceding unsigned comment added by Asidepa (talk • contribs) 20:59, 7 August 2015 (UTC)

Hi, and thanks for your interest. Well, I have (somewhere!) the code and can run it again to get the numbers and plot them. Converting the complex impedances to reflection coefficient is a quick line of code, so in principle plotting them in that form (thus as they'd appear on a Smith chart) would be simple. What is less simple is coming up with the "graph paper" of a Smith chart with grid lines (and labels) for constant resistance and reactance, to plot it over. And in order for a plot in that form to be useful, you'd also have to make marks along the locus to indicate which frequency each point along the locus refers to, and my software isn't set up to do that (or to figure out the most appropriate density of those labels which varies over the plot). That would be a substantial amount of programming and I'm not sure I see a strong motivation for plotting on a Smith chart. If the intention is to see the mismatch of a 'nearly' half-wave dipole off-frequency, then this could also be done using a plot of reflection coefficient magnitude (or SWR) versus frequency around the lambda/2 frequency. The other advantage of plotting as reflection coefficient on a Smith chart is that huge impedances approaching infinity are kept on the chart, so this is better for looking at the big picture (including when the length ≈ lambda and it becomes antiresonant). But when the length reaches 3/2 lambda again, the impedance winds around to values not far from the 1/2 lambda impedance and the plot could get messy.

So in conclusion, I don't see the value of plotting it on a Smith chart given the hassle. But if YOU would like me to export the raw data (for instance in an ASCII file) to plot yourself, I would do that. Or I could rather easily produce a plot in a somewhat different form (such as |Γ| or SWR) versus antenna length (or equivalently, frequency for a given physical length) if there were a point. Interferometrist (talk) 17:41, 6 September 2015 (UTC)

23.31.97.21 (talk) 16:14, 8 September 2015 (UTC)

Interferometrist, Thanks! Right after I clicked "Save Page," I realized the fallacy of my request. It occurred to me that all Smith charts depend upon the reference impedance, and while 50 Ohms may have a dominant presence, it is not the standard. (Even so, a 50-Ohm chart would have been useful.) Anyway, I was curious what you would say in response.

I now agree that my request is more trouble than it is worth. Thanks for your offer for ASCII data, but I too would have to find a way to plot it. What is easier for me to see the antenna impedance, is to use a lumped element model from this paper . I can easily enter them in SimSmith, which also lets me alter the characteristic impedance.